Piston



- May 13, 1947. GRAHAM 2,420,474

PISTON Filed Sept. 22, 1944 3 Sheets-Sheet l IMF. Grw z/a/m' May 13, 1947. Q R HA 2,420,474

PISTON 4 Filed Sept. 22, 1944 5 Sheets-Sheet 2 I i 13 13 2 &1 \x

QJJLL 14 6 May 13, 1947. E. B: GRAHAM 2,420,474

PISTON Filed Sept. 22, 1944 :s Sheets-Sheet 5 Patented May 13, 1947 PISTON Eric Bradley Graham, North Finchley, London,

England, assignor to Specialloid Limited, London, England Application September 22, 1944, Serial No. 555,320 In Great Britain July 19, 1943 2 Claims.

This invention relates to pistons, and particularly pistons for compression-ignition and other internal combustion engines, and has for its object to provide an improved piston in which means is provided for conducting the heat away from the head of the piston and generally the dissipation of heat from the body of the piston, a particular object of the invention being to provide a construction of piston in which ribs are provided within the skirt of the piston for secur ing the dissipation of heat which would present advantages from the point of view of manufacture in, for instance, the withdrawal of core parts in the. case of cast pistons, and the introduction and withdrawal of dies in the case of forged or pressed pistons.

The invention consists in a piston furnished with a plurality of ribs extending generally in the direction of the axis of the piston constituting two groups which are entirely localised in the portions of the skirt between the gud-geon pin bosses, characterised in this that the thickness of the ribs or additionally or alternatively the depth of the ribs decreases from a position adjacent to the head of the piston in a direction towards the lower extremity of the skirt.

Normally the ribs will commence at a position at or somewhat below the lowermost groove of the ring grooves provided above the gudgeon pin bosses and will continue towards the open end of the piston.

The ribs may be so positioned and dimensioned that in machining the skirt ring groove vents will be left in the groove, thus obviating the need for drilling holes in the base of the groove.

Preferably, from each of the gudgeon pin bosses to the interior of the head of the piston, there extends a rib which substantially throughout its length is of the same width as the external diameter of the gudgeon pin boss.

Optionally this rib is furnished adjacent to the face which is directed towards the axis of the piston with a flange extending from the head to the gudgeon pin boss which may be continued round the lower half of the boss.

In certain cases in accordance with the invention ribs may be provided extending in a direction parallel with the common axis of the gudgeon pin boss across the crown from one side of the piston towards the opposite side.

The median planes of the ribs may be radial or tangential or partly radial and tangential to the piston and the thickness of the ribs or additionally or alternatively the depth of the ribs may decrease from a position adjacent to the 2 head of the piston towards the lower extremity of the skirt.

In certain cases the ribs above referred to may be extended over a portion of or across the interior of the head of the piston.

Alternatively ribs may be provided on the centre portion of the crown or head of the piston independently of the ribs which extend in the direction of the axis of the piston.

Further, on the gudgeon pin boss there may be provided a shoulder through which is formed a hole extending generally tangentially or otherwise to the bearing surface of each of the gudgeon pin bosses and communicating with an oil groove extending a desired distance across the gudgeon pin boss and parallel with its axis to promote lubrication of the gudgeon pin and the bearing provided for it by the gudgeon pin boss.

The invention extends to pistons, the heads of which are unrecessed as well as to pistons in which the head is recessed to provide a combustion chamber and in certain cases also recesses into which the heads of the valves of the engine will enter.

In certain constructions in accordance with the invention, the pistons are provided with inserts of austenitic iron or other material which may have a coefficient of expansion to heat which is substantially the same as that of the material forming the body of the piston or which has a desired relation to but differs from the coefficient of expansion to heat of the material forming the body of the piston as described, for instance, in U. S. specification No. 2,255,006.

The insert may be in the form of a ring in which are provided grooves for the accommodation of the compression rings and the opposite extremities of the ring may be provided with flanges formed to assist in securing a satisfactory grip between it and the piston, as described in British patent specification No. 557,070.

Further in accordance with the invention the bosses may each be furnished with a liner which may be of austenitic iron or steel or other material selected in accordance with its wearing or heat conducting properties, as described in British patent specification No. 556,224.

Where the piston comprises inserts formed of a material different from that of the body of the piston, these inserts may be secured therein in the casting or pressing or forging operations used in forming the body of the piston as described in British patent specification No. 556,267.

Optionally, in accordance with the invention, the insert may be arranged to be detachable from the body of the piston and the portion of the piston adjacent the head may be of the same material as the body of the piston and be arranged to be detachable so that when the piston exhibits wear in the vicinity of the compression rings, this portion may be detached and replaced.

The invention is more particularly concerned with pistons, the body of which is formed of a light metal alloy and as examples of such alloys the following may be referred to:

Y alloys high silicon allows such as contain, for instance, a content of silicon between 8 and 25% and, for instance, a content of silicon of approximately 12%, the balance being aluminium or mainly aluminium alloys known as Lo-Ex, the RR range of alloys such, for instance, as RR59, the so-called RAE alloys and cerium aluminium alloys known under the trade-mark Ceral'u'min. Ceralumin C alloy has the following composition:

Cu Not less than 2.0% not more than 3.0% Ni Not less than 1.0% not more than 2.0% Mg Not less than 0.5% not more than 1.0% Fe Not less than 1.0% not more than 1.4% Si Not less than 1.0% not more than 1.4% Ce Not less than 0.05% not more than 0.20%

the balance being aluminium.

The compositions of the other aluminium alloys specifically referred to are as follows:

LO-EX Y alloy Per cent Per cent Si 12 Cu 4 Cu 1 Ni 2 Ni 1 Mg 1.5 Mg 1 Al Remainder Al Remainder RR.59 RAE Per cent Per cent Cu 2.5 Cu 2.0 Ni 1 Ni 3.0 Mg 1.5 Mg 0.5 Fe 1.25 Mn 1.5 Si 1.3 A1 Remainder Al Remainder The invention will be described further in detail and by way of example with reference to the accompanying drawings, in which Figure 1 is a view in elevation,

Figure 2 is a plan View,

Figure 3 is a view insectional elevation on a plane indicated by the line 3-3 of Figure 1 containing the axes of the gudgeon pin bosses,

Figure 4 is an inverted plan view,

Figure 5 is a view in sectional elevation on a plane indicated by the line 55 of Figure 3 perpendicular to the plane containing the axes of the gudgeon pin bosses, and

Figure 6 is a sectional plan view on planes indicated by the line VI-VI in Figure 5 of a piston in accordance withthe invention.

In the drawings, I is the body of a piston, 2 the head formed with grooves 3 for the compression rings and a groove 4 for a scraper ring, 5- are holes passing through the wall. of the piston to permit the passage of lubricating oil, 6- isa groove in the base of which are formed holes 'I also to permit the passage of. lubricating oil, 8 are recesses for the valve heads and 9 is a recess forming a combustion chamber when the piston is in use.

Within the body of the piston there are provided a plurality of tapering ribs I0 extending from a position below the level of the groove for the lowermost compression ring, and terminating somewhat below the level of the groove for the lower scraper ring, or in other words-the skirt ring groove.

In the body of the piston there are provided ribs I I which are of a width not less than the diameter of the gudgeon pin boss and of a depth not less than the length of the portion of the gudgeon pin within the piston extending from the crown of the piston to the gudgeon pin bosses I2. These gudgeon pin bosses are provided with recesses I3 for the engagement of spring rings for securing the gudgeon pin from endwise motion. The'se ribs are substantially throughout their length of the same width as the external diameter of the gudgeon pin bosses.

On the gudgeon pin bosses there are provided shoulders I4 in which are formed oil holes I5.

On the internal surface Of the head of the piston there are provided ribs I6 extending in planes perpendicular to the plane containing the axes of the gudgeon pin bosses, the depth of these ribs progressively decreasing from the internal wall of the piston towards the centre of the crown.

The form of the piston shown in the drawings in consequence of the arrangement; and tapering of the ribs permits of its manufacture by pressing operations and in connection with the drawings it is to be pointed out that the portion I1 is removed by a machining operation in balancing the piston.

I claim:

1. A piston furnished with a plurality of ribs extending generally in the direction of the axis of the piston constituting two groups which are entirely localised in the portions of the skirt between the gudgeon pin bosses, characterised in this that the thickness of the ribs and the depth of the ribs decreases from a position adjacent to the head of the piston in a direction towards the lower extremity of the skirt and, extending from each of the gudgeon pin bosses to the interior of the head of the piston, a rib which substantially throughout its length is at least the same width as the external diameter of the gudgeon pin boss.

2. A piston as claimed in claim 1 in which are provided ribs extending over a portion of or across the interior of the head of the piston.

ERIC BRADLEY GRAHAM.

REFERENGES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS (Addition to No. 634,700) 

